I teach a similar point in my morality classes when I explain that the moral law (natural or Divine) stems from the very attributes of who God is. For example, God demands us to be truthful because God is Truth and we are created in his image and likeness. This is why when we obey the Commandments we are acting in a way which is more fully human. We are actually conforming to the image and likeness of God which we were created in.
This principle that "God is covenant" is very simple to understand. Follow me on two points:
Point I: A covenant is an exchange of persons. In the Old Testament we see God making covenants with His people. God says "I will be your God and you will be my people." This is much more than a contract where an agreement is made. This is a total giving of self where those making the covenant "I am no longer mine, but now I am completely yours." This can best be visibly expressed in marriage, which is a reflection of the Trinity. I give myself to my wife fully and she fully gives herself to me. We pour out our love and our lives for each other. And when husband and wife give themselves to each other in the marital covenant, as Scott likes to say, "nine months later you might have to give it a name." Their love is perfectly poured out to the point that it becomes a third person, a child.
Point II: God is Three Persons. God the Father, for all eternity, generates the Son, who is the perfect image of Himself (the Father). Father and Son give themselves to each other in perfect love. This perfect pouring out of themselves to each other (this covenant) is a third person, the Holy Spirit. God is, in his very being, covenant!
More later on how that plays itself out in the economy of salvation.